This invention relates to security documents or tokens, such as banknotes, travellers cheques, bonds, passports and the like, and to a method of producing same.
The use of transparent windows in banknotes is now well known, as exemplified by PCT/AU82/00135 (WO 83/00659) Improved Banknotes and the Like, as is their use as a carrier for security features. One of these features is a transitory image of the type described in PCT/AU94/00302 (WO 94/29119) Embossing of Banknotes. The transitory nature of the image produced by embossing relies on the properties on the transparent polymer film, including excellent transparency/clarity at most viewing angles, and high gloss or reflective characteristics when viewed perpendicular to a light source, as is observed with a mirror.
It is an object of the present invention to provide an improved security feature which includes an additional level of complexity, making the security feature more difficult to reproduce or copy.
The invention provides a security document or token, including a substrate, said substrate having a security device including a first embossing of the substrate having a predetermined feature, and a second embossing of smaller dimensions formed on said predetermined feature of said first embossing, said first embossing being formed to hide and reveal said second embossing at predetermined viewing angles.
In other words, the security device includes macro-embossing of the substrate and micro-embossing of a portion of the macro-embossing, the macro-embossing functioning to hide and reveal the micro-embossing at predetermined viewing angles.
By forming a second embossing or micro-embossing on the first embossing or macro-embossing, the first embossing or macro-embossing hides and reveals the secondary embossing or micro-embossing at predetermined viewing angles, and in this way provides a security feature which is then able to be produced by high-level security producers at a reasonable price, while being extremely difficult for an average security producer or counterfeiter to reproduce or simulate. The security feature is optically variable, but is nevertheless easy for the person in the street to use to identify a genuine document.
The substrate is preferably a polymer substrate, such as a laminated polymer substrate of the type used in the production of banknotes in Australia and other countries. The first embossing is preferably formed in a transparent portion of the substrate, although acceptable results can be achieved by forming the embossed portion in other regions of the substrate.
In a preferred form of the invention, the secondary embossing is preferably applied to the sides or lower portions of the first embossing.
By using the transparent portion of the polymer substrate, the first embossing is able to hide and reveal the finer second embossing at various viewing angles by using the gloss and transmission properties of the transparent substrate rather than the traditional reflection and absorption properties of printed media.
In a simple embodiment, the macro-embossing may comprise embossed array of lines formed in the substrate, the lines having a predetermined height H and a predetermined spacing S. The height H may vary from a minimum of about 5 microns to a maximum corresponding to the maximum embossable height of the substrate. The spacing S depends on the height and the ratio S:H is typically from about 6:1 to 2:1. The micro-embossing may be formed as lines or dots on the sides of the embossed lines such that the secondary embossed lines are hidden by the primary embossed lines other than at a predetermined range of angles. The secondary lines or dots are embossed to a height to the order of about 2 microns to about 20 microns which causes the clear substrate to appear matt at the predetermined viewing angles. If desired, lower portions of the macro-embossing, or portions of the substrate between adjacent macro-embossings, can be micro-embossed, either in addition to the sides, or as an alternative thereto.
In a preferred embodiment, the macro-embossing comprises lines having a height of from about 5 xcexcm to 3 xcexcm at a spacing of about 10 xcexcm to 100 xcexcm, and preferably a height of about 10 xcexcm to about 25 xcexcm and a spacing of about 30 xcexcm to 100 xcexcm. The upstanding lines created by the macro-embossing are micro-embossed with lines or dots on their sides in a manner which causes the clear substrate to appear matt at viewing angles of about 50 to about 45xc2x0 to the surface of the substrate. The micro-embossing may be configured to form composite shapes, portraits, or any other recognisable device.
The macro and micro-embossing can be performed as part of the printing process and is particularly adapted to the intaglio printing process. Such processes are more clearly described in our prior application WO 94/29119.
The invention further provides a method of producing a security document or token, including forming an embossed security device having a predetermined feature in the substrate, and further embossing predetermined feature with a smaller embossing, such that the embossed security device hides and reveals the smaller embossing at predetermined viewing angles.
The security device is preferably embossed to a height of about 10 to 30 microns, and the sides of the embossing are in turn embossed to a height of about 2 to 20 microns the further embossing being positioned so that the first embossing hides and reveals the secondary embossing at predetermined viewing angles.